1. Field of the Invention
The present invention relates to a haulage vehicle.
2. Description of the Related Art
There has been known a dump truck with a vessel provided to be able to rise and fall on a vehicle. The dump truck transports a large amount of transportation objects such as crushed rocks, earth, sand and so on loaded in the vessel. The dump truck is provided with a hoist cylinder that is telescopically provided between the vessel and the vehicle and that extends to tilt the vessel when discharging the transportation objects from the vessel, as described in International Application Publication No. WO2008/099691.
The hoist cylinder is connected at its lower end with a hoist shaft provided in the vehicle and is connected at its upper end with the vessel by means of a pin. The hoist cylinder has a rod head disposed at its lower end, the rod head is provided with a bore through which the hoist shaft passes, and a cylindrical bushing is arranged in the bore.
The hoist shaft is mounted on the rod head through the cylindrical bushing. The inside diameter of the bushing provided on the rod head is set to be smaller slightly than the outside diameter of the hoist shaft.
The hoist shaft supports the dead weight of those including the vessel and the hoist cylinder. That is, the hoist shaft supports the load directed downward (toward the ground under the vehicle). In this state, a tight contact is held between an internal surface upper part of the bushing and a surface upper part of the hoist shaft, and this gives rise to a problem that it is unable to supply lubricant to the tight contact portion between the hoist shaft and the bushing and hence, that the upper parts of the hoist shaft and the bushing abrade easier than other parts thereof.